1. Field of the Invention
The present invention generally relates to optical switching. More particularly, the present invention relates to a micro-electro-mechanical-system optical switch having a passive latching system.
2. Technical Background
The primary goals of communications technologies have always included the improvement of transmission fidelity, the increase of data rates, and the increase of distance between relay stations. The speed at which light travels and its potential to address all of these concerns logically led to attempts at optical communication. Early experiments with optical communications suggested the feasibility of modulating a coherent optical carrier wave at very high frequencies, but were commercially impractical because of the installation expense and the tremendous cost of developing the necessary components. The combination of semiconductor technology, which provided the necessary light sources and photodetectors, and optical wave guide technology, however, eventually enabled the development and application of optical fiber-spaced systems despite these initially perceived difficulties.
Optical networking involves the management and coordination of various functions such as optical transport and optical switching. Earlier approaches to optical switching actually involved the conversion of optical signals into electrical signals and switching of the electrical signals. This type of electrical/optical conversion proved to be both difficult to implement and costly due to the required transformation into and out of the electrical domain. As a result, more recent approaches have attempted to perform switching in the optical domain.
Optical switching in the networking context presents its own set of unique concerns. For example, in order to efficiently manage the increasing number of optical signals and wavelength channels, optical switches must be significantly reduced in size. Micro-electro-mechanical-systems (MEMS) have recently been developed based on semiconductor processes, and applied in the areas of medicine, life science, sensors, aerospace, micro-satellites and data storage. MEMS technology allows conventionally large components to be reduced to sizes not previously available. While some attempts have been made at applying MEMS technology to optical switching in the networking context, certain concerns such as reliability and power supply still remain.
In fact, reliability of optical cross connect switches is at the forefront of the development of optical networking. Specifically, conventional optical switches have not adequately addressed the issue of latching, and the result has been a considerable decrease in reliability. For example, to ensure the reliability of a MEMS switch, it is best that the reflective element be latched so that it stays in the xe2x80x9conxe2x80x9d or the xe2x80x9coffxe2x80x9d position when power is not being applied. This is known as xe2x80x9cpassive latchingxe2x80x9d. Without latching, external forces such as earthquake tremors and foreign object interference could cause the reflective element to be jarred out of its desired position. Furthermore, active latching systems require dedicated power and control. Accidental power outages can therefore cause these systems to malfunction, thereby raising additional reliability concerns. Thus, active latching systems add to the overall cost and complexity of the switching system. It is therefore desirable to provide an optical switch using MEMS technology that has a passive latching system.
In accordance with the present invention, a micro-electro-mechanical system (MEMS) optical switch is provided. The switch has a reflective element and a switch actuator for moving the reflective element to a first position based on a switching signal. The optical switch further includes a passive latching system coupled to the switch actuator, where the passive latching system maintains the reflective element in the first position when the switching signal is discontinued. The use of a passive latching system improves reliability, reduces costs, and enables the optical switch to serve as a viable alternative to conventional switching devices.
Further, in accordance with the present invention, an optical switch passive latching system for maintaining a reflective element in a first position when a switching signal is discontinued is provided. The latching system has a first magnet configuration coupled to a first portion of a switch actuator. A second magnet configuration is coupled to a second portion of the actuator such that a magnetic force biases the magnetic configurations together when the reflective element is in the first position and the switching signal is discontinued. The use of magnets provides an inexpensive, passive approach to improving reliability by latching.
In another aspect of the invention, a method is provided for switching a reflective element between a first position and a second position based on a switching signal. The method includes the step of moving the reflective element from the second position to the first position based on an electrostatic force between a first electrode and a second electrode. The reflective element is maintained in the first position when the switching signal is discontinued based on a magnetic force between a first magnet configuration and a second magnet configuration. The magnet configurations are coupled to the electrodes. The method further provides for moving the reflective element from the first position to the second position based on a spring force between the electrodes and based on the switching signal. The switching signal reduces the magnetic force between the magnetic configurations to a predetermined forced threshold. In a preferred embodiment, the reflective element is maintained in the second position when the switching signal is discontinued based on a system equilibrium.
It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute part of this specification. The drawings illustrate various features and embodiments of the invention, and together with the description serve to explain the principles and operation of the invention.